VFD Harmonics

Harmonics is lesser known subject causing non-quantified amount of losses.

1. Passive HF are cost effective but doesn't suppress the levels entirely.
2. Passive HF + Active HF (at Point of common Coupling [PCC]) will be economical and lesser than Active HF completely.
3. Active Filters are assured way to mitigate Harmonics below 5%, but cost factor plays the role.
4. Using VFD drives with minimum 18 pulses and above (MV Drives).
5. Quantify < than 5% losses & < than 10% losses and take decision to go for heavy filtering or not. Both are IEEE 519 guidelines.

As a VFD slows down the THD goes up but the total harmonic current goes down. So there is only one point of concern, full speed. If you meet IEEE 519 at full speed you are good to go at any lesser speed point.

The best way to mitigate power harmonics is with an active filter solution. No matter how low or high the load (VFD) runs at an active mitigation solution is best. There are many non-active solutions on the market but they all fall flat under varying load conditions most are based on LC filters and need the C component switched out at low load conditions. Power factor is a vital consideration when looking at any harmonic mitigation.

If you are selecting a VFD for a squared torque application, then you could select a lightly duty variable frequency drive. But remember you are then not supposed to increase the speed beyond the designed fan/motor speed.

Currently, most of the oil pump, water pump and air compressor at a constant speed motor drive state, as will account for an absolute majority of the non-governor speed motor into operation, its power consumption varies with the load size, you can save a lot of energy, will produce significant ...

I suggest to use a 6 pulse drive and use a harmonic device as an adder. In today's world the variable frequency drive faces many potential problems. Power failures, lighting strikes, shorts, etc. If a VFD fails for any reason, a replacement VFD can be had at any local distributor within hours. If ...

It is possible to reduce the speed if a 3 phase motor is used with VFD and ultimately reduce the load but the mechanics and desired mixing may then be affected. The best way to change is either replaces the motor with the correct horsepower/kW, use a different ratio gearbox or change mixing ...

If the 100% torque at 5% speed is what you require, then the variable frequency drive must be able of producing the additional voltage drop in the motor feeder cable and the output sine wave filter. Subject to the motor feeder length, the voltage drop at full load could be 10 to 15 volts and the ...